Thermal stretching of cellulose derivative yarn



Patented Feb. 26, 1946 THERMAL STRETCIHNG F CELLULOSE DERIVATIVE YARNRollin F. Conaway, Wilmington, Dcl., asslgnor to E. I. du Pont deNemours & Company, Wilmington, Bet, a corporation of Delaware NeDrawing. Application September 25, 1942, Serial No. 459,739

12 Claims.

This invention relates to a process for the prevention of adherence offilaments of artificial thermoplastic material to each othe while in theplastic state, and still more particularly to a process operative toprevent filaments sticking during the preparation of high tenacity yarnsfrom thermoplastic cellulose derivatives by stretching yarns renderedplastic by a heat treatment, and to the filament treated according tothe process.

This application is a continuation-in-part of application Serial No.387,551, filed April 8, 1941.

In the field of artificial textiles there is an increasing interest inyarns of much lighter tenacity than have heretofore been available. Amethod widely employed for preparing high tenacity yarns consists instretching the preformed filaments of the yarn which have been renderedplastic by an additional treatment such as the applicatlon of solventsand/or of heat. when this method is'employed, there is a tendency forthe individual filaments of the yarn to adhere to each other while inthe plastic state and thereby form coarse monofils which are generallyundesirable in the textile industry. One of the important problems,therefore, in the preparation of high tenacity yarns by the stretchingof yarns in a plastic state is to prevent the sticking oi filamentsduring the stretching operation. This problem is particularly acute inthe stretching of thermoplastic yarns of cellulose derivatives, thefilaments of which are softened by the thermal process by heat alone, asin Niogret, U. 8. Patent No. 1,921,426.

An object of this invention is to provide a process which will serve toovercome the difilculty oi sticking filaments encountered during thestretching of yarns of thermoplastic cellulose derivatives. A furtherobject is in the provision of filaments of thermoplastic cellulosederivatives, which have been treated to prevent sticking during thestretching thereof. A still further object resides in a process forforming high tenacity yarns of thermoplastic cellulose derivatives whichyarns are free of stuck filaments. A still further obiect is to providea. process for preparing high tenacity yarn free of stuck filaments,from heat-softened yarn comprised of preformed iilaments of celluloseacetate. These and other obiects will more clearly appea hereinafter.

The objects of this invention are accomplished by applying to yarns ofpreformed filaments of thermoplastic cellulose derivatives, 9. liquidcomposition containing essentially a dissolved or dispersed inert solidhaving a melting or softenin point above the thermal stretchingtemperature of the yarns, said composition being substantially inert tothe cellulose derivatives under the operating conditions, that is,having no softening action on the yarn either at low or elevatedtemperatures. The treated yarn is then optionally conditioned to removeall or a portion of the liquid and is heat-softened, and then stretchedwhile in the softened state. Finally the composition is removed from thehigh tenacity yarn by any convenient method, as by washing, for example.

For purposes of this invention there may be employed any solidsubstance, or potentially solid substance, the melting or softeningpoint of which is above the thermal stretching temperature of the yarnundergoing treatment, and which in addition does not, under theoperating conditions. have a softening or dissolving effect on, and isotherwise chemically inert with respect to, the cellulose derivative ofwhich the yarn is comprised. Preferred inert solids are thewater-soluble salts of inorganic and organic acids such as the sodium,potassium, and lithium sulfates. chlorides. and bromides; sodiumsuliocyanate, magnesium sulfate, calcium chloride, barium nitrate,sodium and potassium alums, beryllium chloride, copper sulfate, calciumacetate. sodium formate, sodium propionate, sodium lactate, and sodiumglycolate, which are applied in aqueous solution. Substantiallywater-insoluble solids such as talc, bentonite, chalk, fullers earth,starch, carbon black, synthetic resins, and the like can also beemployed, and are applied most conveniently a aqueous dispersions.Solventand dispersing media other than water, which do not have asoftening eil'ect on thermoplastic cellulose derivatives, can likewisebe employed, either singly, in homogeneous mixture, or in the form ofemulsions.

In most instances, the addition to the liquid composition of a bindingagent which is inert, that is, does not exert a softening action on thecellulose derivatives, improves the process by enabling more uniformtretching to be carried out and by providing a protective covering forthe yarn. It is preferred to use those colloidal binding and protectiveagents which also function as crystallization inhibitors for thewatersoluble salts employed. Examples of suitable colloidal bindingagents, yarn protective agents and/or crystallization inhibitors areglucosldes such as saponin, naturally occurring gums such gum arable,protein materials such as glue and gelatin, polyvinyl alcohol,water-soluble cellulose derivatives such as water-soluble methyl andhydroxyethyl cellulose, and pectin.

The preferred antisticking compositions of this invention are preparedby dissolving the watersoluble salt and the colloidal binding agent inwater to form a homogeneous solution. A small amount of a wetting agent,such as the sodium salt of long chain alkyl sulfates, may also be addedto the solution in order to improve the uniformity of wetting of theyarn by the solution. The concentration of constituents in the solutionvaries with the type of yarn, nature of stretching conditions, extent ofstretching, composition of the constituents in the solution ofantisticking composition, and method of applying the finish to the yarn.In general, the optimum conditions are obtained with aqueous solutionscontaining from 0.5 to of the salt, 0.1 to 2% of water-soluble colloidalbinding agent, and 0.01 to 1% of a wetting agent.

The drying or conditioning of the yarn prior to stretching by thethermal procedure is optional and depends on the type of thermalstretching unit employed. In most cases more uniform yarn properties areobtained with dry yarn, whereas in a few cases wet or moist yarnproduces more uniform stretching conditions and stretched yarns withimproved physical properties.

The following examples illustrate the invention. Parts are by weight.

Example I This example illustrates the use of sodium chloride andsaponin as the antisticking composition for cellulose acetate yam whenthe speeds and extent of stretching are relatively low.

An aqueous solution of sodium chloride and saponin was prepared bydissolving 1 part of sodium chloride and 1 part of purified saponin in98 parts of water at room temperature. The resulting homogeneoussolution was applied to 150 denier-100 filament cellulose acetate yarnhaving 3 turns/inch twist by means of a size roll at a linear yarn speedof l5 ft./min., and dried. The resulting dry yarn, which contained 3% ofantisticking composition on a dry basis. was stretched 1000% by passingthe yarn into a heated chamber maintained at a temperature of 218 C. andstretching the heat-softened yarn at a wind-up speed of 110 ftJmin. Theresulting stretched yarn possessed a tenacity of 2.3 g./den., and wasfree from filament sticking. When the yarn was stretched under the sameconditions without applying an antisticking finish, the resultingstretched yarn was stuck badly and possessed the characteristics of amonofil.

Example II This example illustrates the use of the sodiumchloride-saponin size on fine denier cellulose acetate yarn at rapidstretching rates.

An aqueous solution containing 2 parts of sodium chloride and 2 parts ofsaponin in 96 parts of water was prepared and applied to 300 denier- 100filament cellulose acetate yarn having 3 turns/inch twist by means of asize roll at a linear speed of 60 ft./mm. The yarn. containing 1.0%antisticking composition. was dried at room temperature and passed intoan electrically heated chamber maintained at a temperature ofapproximately 225" C. The heat-softened yarn was stretched 1070% at awind-up speed of 200 ftJmin. The 28 denier-100 filament stretched yarnpossessed a tenacity or 3.8 g./den.. and had a soft, pleasant handindicating the absence of asaasoe filament sticking. The filaments ofthe yarn separated completely from one another on breaking, indicatingthe absence of filament sticking. Cellulose acetate yarn stretched underthe same conditions in the absence of an antisticking finish was stuckbadly and in general possessed the properties of a monofil.

Example III This example illustrates the use of the sodiumchloride-saponin antisticking composition on cellulose acetate yarnstretched in a liquid medium in which the sizing and stretchingoperations were carried out continuously without an intermediate dryingoperation.

An aqueous solution containing 8 parts of sodium chloride and 2 parts ofsaponin dissolved in parts of water was prepared and applied to 300denierfilament cellulose acetate yarn possessing 3 turns/inch twist bymeans of a size roll at a linear speed of 25 ft./min. The wet yarn,containing 3.4% antisticking composition on a dry basis, was then passedinto a liquid bath of molten solder composed of equal parts of tin andlead, maintained at a temperature of 238 C., and the yarn stretched 515%at a wind-up speed of 130 it./min. Theresulting washed and dried 58denier-100 filament yarn possessed a tenacity of 3.2 g./den., a soft andpleasant hand, and separated completely into filaments on breaking.

Example IV This example illustrates the use of the sodiumchloride-saponin antisticking composition on large denier celluloseacetate yarn stretched in hot liquid media at high stretching ratios.

An aqueous solution containing 12 parts of sodium chloride, 2 parts ofsaponin, and 86 parts of water was prepared and applied to 660 denier-66 filament cellulose acetate yarn containing 3 turns/inch twist bymeans of a sizing roll at a linear speed of 20 ft./min. The wet yarn,containing 5.0% of antisticking composition, was passed into a hotliquid bath of solder (50% tin- 50% lead) maintained at a temperature ofapproximately 245 C. under a yarn tension of 8 grams. The heat-softenedyarn was stretched 1250% at a wind-up speed of 250 i't./min. The washedand dried 53 denier yarn possessed a tenacity of 3.1 g. /den., and wasfree from filament sticking since the filaments separated on rubbing orbreaking the yarn.

Example V This example illustrates the use of the sodiumchloride-saponin antisticking composition containing a small amount of awetting agent in the stretching of large denier cellulose acetate yarnwith hot liquid baths at high stretching ratios.

An aqueous solution containing 10 pans of sodium chloride. 2 parts ofsaponin, 0.1 part of "Lorol" sodium sulfate ("Lorol" refers to theresidue of commercially available mixed primary alcohols containing 10to 18 carbon atoms), and 87.9 parts of water was prepared and placed inconventional sizing equipment. 2400 denierfilament cellulose acetateyarn containing 3.

turns/inch twist was passed over the size roll coated with thecomposition at a linear speed of 3 ft./min. The wet yarn containing 7.0%antisticking composition was passed into a hot liquid bath of moltensolder (50% tin-50% lead) at a temperature of approximately 240 C. undera tension of 20-25 grams. The heat-softened yarn was stretched 15'70% ata wind-up speed of aseasce ftJmin. The washed and dried 150-denier yarnpossessed a tenacity of 2.2 g./den. It possessed a soft, pleasant handand the filaments separated completely on breaking the yarn.

Example VI This example illustrates the use or the sodiumchloride-saponin antisticking composition on cellulose acetatepropionate yarn.

A 150 denier-38 filament mixed ester yarn prepared i'rom celluloseacetate propionate containing approximately 2.5% of combined propionicacid and 52% of combined acetic acid was passed over a size rollcontaining the same antisticking composition as employed in Example V,at a linear speed of 22 it./min. The wet yam, containing 6.0% ofantisticklng composition, was passed into a hot liquid (50% tin-50% leadsolder) bath maintained at a temperature or 240 c. The heat-softenedyarn was stretched 600% at a wind-up speed or 132 ft.,/min. Theresulting stretched yarn possessed a tenacity of 2.5 g./den., and asoft, pleasant hand indicating that the filaments were not stuck to eachother.

Example VII This example illustrates the use oi the sodiumchloride-saponin antisticking composition on cellulose nitrate yarn.

An aqueous solution containing 8 parts of sodium chloride, 2 parts ofsaponin. and 90 parts of water was prepared and placed in the sizingequipment. A 550 denier-60 filament cellulose nitrate yarn spun fromcellulose nitrate with a nitrogen content of 11.06% was passed over thesize roll coated with antisticking solution, at a linear speed 01' 50it./min. The yarn was allowed to dry at room temperature beforestretching. The dry yarn was passed through a hot air stretching chambermaintained at a temperature of 186 C. at an in-put speed of 19 it./min.and a wind-up speed of 100 it./min. The resulting 105 denier stretchedyam possessed a tenacity or 2.65 g./den. and a soft, pleasant handindicating that the filaments of the yarn had not been (used to eachother during the stretching operation.

Example VIII This example illustrates the use of glue in theantisticking composition in place oi saponin as the water-solublecolloid.

An aqueous solution containing 20 parts sodium chloride, 6 parts of hideglue, and 74 parts oi water was prepared and placed in the sizingequipment. A 300 denier-100 filament cellulose acetate yarn was passedover the size roll at a linear speed of 50 it./min. The yarn containing14% of antisticking composition was dried at room temperature andstretched 500% by passing the dry yarn through a heated air chambermaintained at a temperature of 222 C. at an in-put speed oi it./min. anda wind-up speed 01' 50 it./min. The resulting purified yarn had atenacity of 2.9 g./den. and a very soft hand. The filaments in this yarncould be separated by merely untwisting the yarn, indicating the absenceoi stuck filaments.

Example IX This example illustrates the use of gelatin as thewater-soluble colloid in the antisticlring composition.

An antisticking solution containing 4 parts of ,sodium chloride, 4 partsof gelatin, and 92 parts of water was prepared and placed in the sizingequipment. A 300 denier-100 filament cellulose acetate yarn was passedover the size roll coated with the antisticking solution at a linearspeed of 50 itJmin. The yarn, containing 9.0% of antistickingcomposition, was dried at room temperature and stretched 600% by passingthe dry yarn through a heated chamber maintained at a temperature of 228C. in which the in-put speed was 20 ft./min. and the out-put speed 120itJmin. The resulting stretched yarn, after washing to remove thefinish, possessed a tenacity oi 2.9 g./den., and was free from stuckfilaments.

Example X This example illustrates the use of gum arable as thewater-soluble colloid in the antlsticking composition.

An antisticking composition containing 20 parts of sodium chloride, 4parts of gum arable, and 76 parts of water was prepared and placed inthe sizing equipment. A sample of 300 denierfilament cellulose acetateyarn was passed over the size roll at a linear speed of i0 ft./min. Thewet yarn containing 10% of antisticking composition was passed through aheated chamber maintained at a temperature of 222 C. at an in-put speedof 10 ft./min. and a wind-up speed of 50 it./min. The resulting yarn,which had been stretched 500%, possessed a very soft hand and a tenacityof 3.0 g./den. The filaments in the yarn could be separated byuntwisting the yarn. indicating the absence of filament sticking.

Example XI This example illustrates the use of sodium sulfate in theantisticking composition in place of sodium chloride.

An antlsticking composition containing 15 parts of anhydrous sodiumsulfate, 1 part of saponin, and 84 parts of water was prepared andplaced in the sizing equipment. A 300 denier-100 filament celluloseacetate yarn was passed over the sizing roll and into a heatedstretching chamber maintained at a temperature of 220 C., at a rate of10 ft./min. The yarn. containing 8.6% ant-isticking composition, wasstretched 500% in the chamber and wound on a positively-driven bobbin ata speed of 50 ft./min. The stretched yarn had a tenacity of 2.8 g./den.and was very soft and free from stuck filaments.

Example XII This example illustrates the use of an antisticking finishin the stretching of delustered cellulose acetate yarn.

An aqueous solution containing 10 parts of sodium chloride, 2 parts ofsaponin, 0.1 part of "Lorol sodium sulfate, and 87.9 parts of water wasprepared and placed in the pan of the sizing equipment. A 300 denier-104filament cellulose acetate yarn delustered with titanium oxide pigmentwas passed over the size roll at a linear speed of 22 it./min The wetyarn, containing 5.8% antisticking composition, was stretched 600% whilepassing through a hot liquid solder (50% tin-50% lead) bath maintainedat a temperature of 240 C. The resulting stretched yarn possessed a softhand and a tenacity of 3.0 8./den. The filaments of the yarn separatedcompletely on breaking, indicating the absence of stuck filaments.

Example XIII This example illustrates an antisticking compositioncontaining calcium acetate and saponin. An aqueous solution of calciumacetate and saponin was prepared by dissolving 6 parts of calciumacetate and 2 parts of saponin in 92 parts of water at room temperature.The resulting homogeneous solution was applied to 300 denier-100filament cellulose acetate yarn by passing the yarn continuously throughapproximately 4 inches of the solution in a size pan at a linear speedof 36 itJmin. The resulting wet yarn was stretched 555% by passing intoan 18- inch molten solder bath heated to a temperature of 238 C. andwinding the heat-softened yarn on a bobbin at a wind-up speed of 200ftJmin. under a tension of 6 grams. The resulting 55 denier yarn had atenacity of 3.0 g./den., elongation of 5.5%, and fibrillated completelyon breaking, indicating the absence oi filament sticking.

Example XIV This example illustrates an antisticking compositioncontaining calcium acetate and polyvinyl alcohol.

An aqueous solution of calcium acetate and polyvinyl alcohol wasprepared by dissolving 1.2 parts of calcium acetate and 0.1 part ofwatersoluble polyvinyl alcohol in 98.7 parts of water at roomtemperature. The resulting homogeneous solution was applied to 300denier-100 filament cellulose acetate yam by passing the yarncontinuously through approximately 4 inches of the solution in a sizepan at a linear speed of 40 ft./min. The wet yarn was passed over thesurface of a pre-drier 36 inches in length, heating by steam to atemperature of 116 C. in order to dry the impregnated yarn. The dry yarnwas passed continuously into a vertical heated tube 36 inches in lengthheated to a temperature of 245 C. The heat-softened yarn was stretched555% in the heated air column under a tension of 6 grams and wound on abobbin at a wind-up speed of 225 ft./rnin. The resulting stretched 55denier yarn, after washing possessed a tenacity of 3.1 g./den., anelongation of 5.0%, and a soft, pleasant hand indicating the absence offilament sticking.

Example XV This example illustrates the use of an antistickingcomposition containing sodium formate and saponin.

An aqueous solution sodium formats and saponin was prepared bydissolving 6 parts of sodium formate and 1 part of saponin in 93 partsof water at room temperature. The resulting homogeneous solution wasapplied to 300 denier- 100 filament cellulose acetate yarn containing 3turns per in h twist by passing the yarn continuously through 4 inchesof the solution in a size pan at a linear speed of 39 it./mln. The wetyarn was dried by passing over a steam heated drier and the dry yarn wasstretched 770% by passing through a vertical air-type stretching unitheated to a temperature of approximately 245 C. under a stretchingtension of 6 grams and a wind-up speed of 240 ft/min. The resulting 40denier yarn had a tenacity of 3.4 g./den., an elongation of and a. soft,pleasant hand indicating the absence of filament sticking.

Example XVI This example illustrate the use of an antistickingcomposition containing sodium propiomate and saponin.

An aqueous solution of sodium propionate and saponin was prepared bydissolving 9 parts of sodium propionate and 1 part of saponin in 90parts of water at room temperature. The resulting homogeneous solutionwas applied to 300 denierfilament cellulose acetate yarn by passing theyarn continuously through approximately 4 inches or the solution at alinear speed 01 36 ft./min. The resulting wet yarn was passed into an18- inch molten solder bath, the same as in Example XIII above, heatedto a temperature of 242 C. and stretched 555% under a tension of 9 gramsand a wind-up speed of 200 rtJmin. The resulting high tenacity yarn hada yery soft and pleasant hand, indicating the absence of filamentsticking.

Example XVII This example illustrates the use 01' an aqueous dispersionof talc as the antisticking composition.

An aqueous dispersion containing 2 parts of saponin. 8 parts of finelydivided tale in which a major portion of the particles had a particlesize of 1 to 15 microns, 0.5 part of Gar-dine? WA (sodium salt oftechnical sulfated dodecanol-i) and 89.5 parts 01' water was prepared byadding the tale to the aqueous solution oi the other constituents withrapid agitation. The resulting dispersion was applied to 300 denier- 100filament cellulose acetate yarn by passing the yarn continuously throughapproximately 4 inches of the dispersion in a size pan at a linear speedof 36 ft./min. The wet impregnated yarn was passed into an 18-inchsolder bath at a temperature of 242 C., and the heat-softened yarnstretched 555% under a tension of 8 grams and a wind-up speed of 200i't./min. The resulting 55 denier yarn possessed a tenacity of 3.0g./den., an elongation of 5.5%, a soft hand, and an open structureindicating the absence of filament sticking.

Example XVIII This example illustrates the use of an aqueous dispersionof finely divided chalk as the antisticking composition.

The same conditions were employed as in the preceding example, exceptthat the aqueous dispersion contained 8 parts 01' finely divided chalkin place of 8 parts of talc.

Example XIX This example illustrates the use of an aqueous dispersion offuller's earth as the antisticking composition.

The same conditions were employed in this example as in Example XVIIabove. except that 4 parts of fullers earth was employed in thedispersion in place of 8 parts of talc. The resulting stretched yarn washarsh prior to washing, but after washing was soft and open indicatingthe absence of filament sticking.

Example XX This example illustrates the use of an aqueous dispersion offulier's earth and bentonite as the antisticking composition.

In this example the same conditions were employed as in Example XVIIabove, except that 8 parts of fullers earth and 1 part of bentonite wereemployed in the aqueous dispersion in place of the tale. The resultingstretched and washed yarn was soft and open indicating the absence offilament sticking.

Example XXI This example illustrates the use of a solution of GardinolWA (sodium salt of sulfated technical dodecanol-l) in a commercialmixture oi butyl stearate and palmitate.

A composition containing 4 parts of Gardinol" WA and 96 parts of amixture of butyl palmitate and stearate was prepared by adding theasoasee "Gardinol" WA to the synthetic oil mixture with rapid stirringat room temperature. Approximately one-half of the GardinoP' WAdissolved in the oil so that the resulting composition was a dispersionof "GardinoP WA in a solution of Gardinoi WA and butyl stearate andpaimitate. This oil dispersion was applied to 300 denier-100 filamentcellulose acetate yarn by passing the yarn over a size roll coating withthe dispersion at a linear speed of 36 ft./min. The coated yarn waspassed into an 18-inch bath of molten solder at a temperature of 242 C.The heat-softened yarn was stretched 555%, under a stretching tension of8 grams and a wind-up speed of 200 ft./min. The resulting stretchedyarn, after scouring, possessed a soft hand and open structureindicating the absence of filament sticking.

Example XXII This example illustrates the use of an aqueousoil emulsionas an antisticking composition.

An aqueous solution containing 2 parts of "Gardinol" WA, 1 part ofsaponin, 2 parts of sodium propionate, dissolved in 25 parts of waterwas added at room temperature, with rapid stirring, to 25 parts of acommercial mixture of butyl stearate and palmitate. The resultingemulsion was applied to 300 denier-100 filament cellulose acetate yarnby the size-r011 technique, and the coated yarn stretched in the moltensolder bath under the same conditions as in Example XXI above. Thestretched 55 denier yarn, after scouring in an 0.5% soap solution,washing and conditioning, possessed a tenacity of 3.0 g./den., anelongation of 4%, a soft hand, and open structure, indicating theabsence of filament sticking.

It is understood that the above examples are by way of illustration onlyand that the invention is susceptible to wide variation from'the exactmaterials and conditions set forth in the examples. Thus, theanti-sticking composition of this invention is applicable to allthermoplastic yarns and to those types of stretching procedures wherethere is a tendency for the surface of the individual filaments tobecome suiliciently soft or plastic to cause them to adhere to oneanother.

The concentration of the inert solid employed may vary between widelimits and is determined by the type of yarn employed, the conditions ofsizing and stretching, and the extent of stretching. If the rate andextent of stretching of cellulose acetate yarn is low, a concentrationof 1% of solid, such as sodium chloride, may be sufllclent. On the otherhand, if the rate of stretching is high, which necessitates the use ofhigher temperatures in the stretching chamber, and the extent ofstretching is high, such as in the order' of 800-2000%, it may benecessary to increase the concentration of the solid to as much as 20%.Concentrations of solid in the range of 0.5% to 5% are in most casespreferable.

The concentration of binding agent employed in the composition dependson the concentration of salt which in turn is governed by the factorsmentioned above. With concentrations of the inert solid in the order of0.5% to 5%, concentrations of binding agent in the order of 0.1% to 2%are sufiicient. When the concentration of solid is increased to it maybe necessary to increase the concentration of binding agent to as muchas 6%. The preferable concentration of binding agent is in the range of0.01% to 2%, but the concentration may be increased to 5.0% or higherwithout deleterious effects.

The wetting agent added to the solution may be any of th standard typesof surface-active agents that meet the basic requirements of the otheringredients in the composition. The materials which have been found tobe most eifective are the sodium salts of the long-chain aliphaticacids, such as stearlc acid, and the salts of the sulfonates andsulfates of the corresponding alcohols of these acids, such as Lorol"sodium sulfate. The concentration of surface-active agents employeddepends on the efliciency of the material as well as th type ofantisticking composition, yarn, and sizing conditions employed. Ingeneral, a concentration in the order of 0.01% to 1.0% is most desirablebut can be increased to higher values without deleterious effects.

Any of the standard methods of sizing, such as by passing the yarnthrough the solution or over a sizing roll, can be employed to apply theantisticking solution to the yarn. The concentration of antlstickingfinish on the yarn, calculated on a dry basis, may vary between widelimits, depending on the chemical and physical nature of the yarn andthe stretching conditions. When the extents and rates of stretching ofcellulose acetate yarn are low, a solids concentration of 1% of theantlsticking finish on the yarn may be adequate to prevent the fusing offilaments. Under more drastic conditions in which large denier yarns arestretched in the order of 2000% at rapid rates and high temperatures,concentrations of the antisticklng finish on the yarn, calculated on adry basis, may be as high as 10% in order to prevent sticking offilaments during the stretching operation; If the concentration offinish on the yarn becomes too high and the uniformity of application isnot adequate, diiiiculty is encountered with non-uniform stretchingconditions so that, for" most operating conditions, concentration offinish in the order of 1% to 10% on the yarn is preferred.

The treated yarn can be passed into the stretching chamber in either awet, moist, or dry condition. When the yarn enters the stretching mediumin a wet state, the application of the antisticking composition and thestretching procedure is preferably carried out in one continuousoperation. When the yarn is dry or moist, the operation may be eithercontinuous or discontinuous. If the operation is continuous, the yarn ispassed through conditioner or drier to lower the moisture content tothedesired extent prior to passing through the stretching chamber. If theapplication of the antlsticking composition is carried out separately,the yarn can be dried or conditioned in suitable ovens or chambers priorto stretching. The advisability of using the continuous or discontinuousprocess depends on a number of factors, among which the most importantare the type of yarn employed and the conditions of stretching. Undersome conditions of stretching, better results are obtained with moist orwet yarn, whereas under other conditions, the uniformity of stretchingis improved by the use of essentially dry yarns.

The antisticking finish may be removed from the stretched yarn bysuitably washing either immediately following the stretching operationor after some subsequent textile operation.

The procedure of coating the yarn with the composition of this inventionprior to stretching in order to prevent the sticking of filamentsproduces stretched yarns with high tenacities and.

proved yarn properties, such as higher knot strength, which are highlydesirable and, in most cases, essential in yarns for general textileuse. The procedure is also useful in the thermal treatment of yarnscomposed of multiple filaments of thermoplastic materials, such aspolystyrene, Vinyon, vinyl esters, vinyl ethers, methacrylates andnylon, in addition to the cellulose derivatives. The thermoplasticcellulose derivatives may be classified broadly as esters, ethers, mixedesters, mixed ethers, and mixed ether-esters, such as cellulose acetate,nitrate, propionate, butyrate, acetate propionate, acetate butyrate,ethyl cellulose, benzyl cellulose, ethyl lauryl cellulose, ethylcellulose acetate, and methyl cellulose propionate.

I claim:

1. In the process for producing high tenacity filaments, yarns, andthreads of thermoplastic cellulose derivatives wherein preformedfilaments of thermoplastic cellulose derivatives are softened by heatand stretched while in the softened condition, the improvement whichcomprises applying to the filaments prior to heat treating a liquidcomposition comprising an inert solid having a melting or softeningpoint above the thermal stretching temperature of the filaments, andheat-treating the filaments to soften the same while retaining saidinert solid thereon whereby to prevent sticking of the filaments whilein the softened condition.

2. In the process for producing high tenacity filaments, yarns, andthreads of thermoplastic cellulose derivatives wherein preformedfilaments of thermoplastic cellulose derivatives are softened by heatand stretched while in the softened condition, the improvement whichcomprises applying to the filaments prior to heat treating a liquidcomposition comprising an inert solid having a melting or softeningpoint above the thermal stretching temperature of the filaments, and aninert water-soluble binding agent, and heattreating the filaments tosoften the same while retaining said inert solid and binding agentthereon whereby to prevent sticking of the filaments while in thesoftened condition.

3. In the process for producing high tenacity filaments, yarns, andthreads of cellulose acetate wherein preformed filaments of celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comprises applying to the filamentsprior to heat treating a liquid composition comprising an inert solidhaving a melting or softening point above the thermal stretchingtemperature of the filaments, and heat-treating the filaments to softenthe same while retaining said inert solid thereon whereby to preventsticking of the filaments while in the softened condition.

4. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments of celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comprises applying to the filamentsprior to heat treating a liquid composition comprising an inert solidhaving a melting or softening point above the thermal stretchingtemperature of the filaments, and an inert water-soluble binding agent,and heat-treating the filaments to soften the same while retaining saidinert solid and binding agent thereon whereby to prevent sticking of thefilaments while in the softened condltion.

5. In the process for producing high tenacity filaments, yarns, andthreads, of thermoplastic cellulose derivatives wherein preformedfilaments of thermoplastic cellulose derivatives are softened by heatand stretched while in the softened condition, the improvement whichcomprises applying to the filaments prior to heat treating an aqueousliquid composition comprising an inert water-soluble salt having amelting point above the thermal stretching temperature of the filaments,and heat-treating the filaments to soften the same while retaining saidinert solid thereon whereby to prevent sticking of the filaments whilein the softened condition.

6. In the process for producing high tenacity filaments, yarns, andthreads, of thermoplastic cellulose derivatives wherein preformedfilaments of thermoplastic cellulose derivatives are softened by heatand stret... :d while in the softened condition, the improvement whichcomprises applying to the filaments prior to heat treating an aqueousliquid composition comprising an inert water-soluble salt having amelting point above the thermal stretching temperature of the filaments,and an inert water-soluble binding agent, and heat-treating thefilaments to soften the same while retaining said inert solid andbinding agent thereon whereby to prevent sticking of the filaments whilein the softened condition.

'7. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments of celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comprises applying to the filamentsprior to heat treating an aqueous liquid composition comprising an inertwater-soluble salt having a melting point above the thermal stretchingtemperature of the filaments, and heat-treating the filaments to softenthe same while retaining said inert solid thereon whereby to preventsticking of the filaments while in the softened condition.

8. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments of celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comprises applying to the filamentsprior to heat treating an aqueous liquid composition comprising an inertwater-soluble salt having a melting point above the thermal stretchingtemperature of the filaments, and an inert water-soluble binding agent,and heat-treating the filaments to soften the same while retaining saidinert solid and binding agent thereon whereby to prevent sticking of thefilaments while in the softened conditlon.

9. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments of celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvements which comprise applying to the filamentsprior to heat treating an aqueous liquid composition comprising an inertwater-soluble salt having a melting point above the thermal stretchingtemperature of the filaments, an inert water-soluble binding agent, anda wetting agent, heat-treating the filament to soften the same whileretaining said inert solid, binding agent and wetting agent thereonwhereby to prevent sticking of the softened filaments, and removing thecomposition from the filaments after stretching.

10. In the process for producing high tenacity filaments, yarns, andthreads, of thermoplastic cellulose derivatives wherein preformedfilaments of thermoplastic cellulose derivatives are softened by heatand stretched while in the softened con.

a,sos,seo

dition, the improvement which comprises app ying to the filaments priorto heat treating an aqueous liquid composition comprising from about0.5% to about 10% by weight of an inert water-soluble salt having amelting or softening point above the thermal stretch temperature of thefilaments, and Iron 0.l% to about 2% by weight of an inert water-solublebinding agent, and heat-treating the filaments to soften the same whileretaining said inert solid and bindin; agent thereon whereby to preventsticking of the filaments while in the softened condition,

11. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments oi celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comrises applying to the filamentsprior to heat treating an aqueous liquid composition compris- ROE-IN F.CONAWAY.

Certificate of Correction Patent No. 2,395,396.

February 26, 1946.

ROLLIN F. CON AWAY It is hereby certified that errors appear in theprinted s ecification of the above numbered patent requiring correctionas follows: Pa e 1, hghter" read higher; page 2, first column, line 67,

mt column, line 14, for xample II, for 60 ft./mm.

read 60fi.lm'in.; and that the said Letters Patent should be read withthese corrections therein that the same may conform to the record of thecase in the Patent Ofice.

Signedand sealed this 14th day of May, A. D. 1946.

[BELL] LESLIE FRAZER,

First Assistant C'ommissiomr of Patents.

a,sos,seo

dition, the improvement which comprises app ying to the filaments priorto heat treating an aqueous liquid composition comprising from about0.5% to about 10% by weight of an inert water-soluble salt having amelting or softening point above the thermal stretch temperature of thefilaments, and Iron 0.l% to about 2% by weight of an inert water-solublebinding agent, and heat-treating the filaments to soften the same whileretaining said inert solid and bindin; agent thereon whereby to preventsticking of the filaments while in the softened condition,

11. In the process for producing high tenacity filaments, yarns, andthreads, of cellulose acetate wherein preformed filaments oi celluloseacetate are softened by heat and stretched while in the softenedcondition, the improvement which comrises applying to the filamentsprior to heat treating an aqueous liquid composition compris- ROE-IN F.CONAWAY.

Certificate of Correction Patent No. 2,395,396.

February 26, 1946.

ROLLIN F. CON AWAY It is hereby certified that errors appear in theprinted s ecification of the above numbered patent requiring correctionas follows: Pa e 1, hghter" read higher; page 2, first column, line 67,

mt column, line 14, for xample II, for 60 ft./mm.

read 60fi.lm'in.; and that the said Letters Patent should be read withthese corrections therein that the same may conform to the record of thecase in the Patent Ofice.

Signedand sealed this 14th day of May, A. D. 1946.

[BELL] LESLIE FRAZER,

First Assistant C'ommissiomr of Patents.

